Van type vehicles for passengers and for cargo are frequently equipped with a sliding side door. Sliding doors are supported and guided by rollers that run in fixed tracks. These sliding doors are generally on the side of the vehicle opposite the vehicle operator's station. To open or close the sliding doors, it is necessary for the vehicle operator to leave the operator's station and either walk around the outside of the vehicle to the sliding door or to cross the inside of the vehicle to the sliding door. Crossing the inside of the vehicle is often difficult or impossible due to cargo or passengers inside the van.
Power systems for opening and closing sliding doors on vehicles have long been considered desirable. Attempts to provide a power system for opening and closing sliding doors have had limited success. The systems have generally been complicated and expensive. Some of these sliding door opening and closing systems have not permitted manual opening or closing of sliding doors when the power system is inoperable for some reason. Other systems have not controlled the position of the door at all times thereby allowing some undesirable free travel.
Sliding door slamming and time requirements for opening and closing have also been problems. Sliding doors which move rapidly must be stopped quickly upon closing. This rapid deceleration places large loads on vehicle structures and causes noise. Acceleration forces that occur when sliding doors are accelerated from stationary states to relative high speeds also exert substantial loads on vehicle body structures that may lead to structural problems. Sliding doors which close gently have tended to move slowly and take excessive time to open and close.